1. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Phase-dependent probe amplitude in the continuous wave regime. The blue line is the PZT voltage, which changed the relative phase between the control and probe field in channel 1. It was swept from 0 to 25 V in 2 s, and a 2π phase change corresponds to about 0.8 s. The control and probe are both continuous LPL light in this experiment. The two figures were taken under very small (1 to 2 nT) but different magnetic fields applied to cancel the residual field in the shields in either Ch1 (a) or Ch2 (b). Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

2. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Dependence of the amplitude of probe pulses in both channels on the relative phase in Ch1 between the control and the probe. The pulse width was 5 ms. The result is similar to that of the CW probe case in the above figure. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

3. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Beam splitter signal for the (a) EIT and (b) self-rotation schemes, respectively. On the left is the result in Ref. 6 and on the right is our LPL results. Due to the amplification effect from self-rotation and optimization of the experiment conditions, the retrieved probe signal in channel 2 is about 50 times the previous CPL result (compared to the same input reference). The width of the pulse is 5 ms. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

4. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Schematics of the experimental setup. AOM, acoustic optical modulator; PZT, piezoelectric transducer; and PBS, polarization beam splitter. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

5. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Numerical calculation shows when the relative phase is ±π/2, the signal reached maxima, and the peak is about 1.7 times in amplitude compared with the original one, which is the amplification from self-rotation. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

6. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Energy levels of Rb87 D1 line represented in the circular and linear polarization basis, respectively. (a) A left and a right circularly polarized light (CPL) couple two ground states |a 〉, |b 〉 and the two excited states. (b) The two CPL are replaced by two linearly polarized light (LPL) beams along x- and y-direction. Correspondingly, the ground states are changed to two superposition states |x 〉 and |y 〉. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

7. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Interference signal between the control and probe in each channel. A half-wave plate at the cell output was added to interfere the control and probe, in order to measure their relative phase. The relative phase at the input of Ch1 was swept, and both channels followed the change indicating that the two channels were still phase coherent under amplification. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

8. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Optical memory for a 6-ms width pulse, with 10-ms storage time. The half-pulse on the left is the leaked pulse (not stored due to the limited optical depth) in Ch1. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

9. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Optical memory for an 80-μs width pulse, with 10-ms storage time. Channel 2 control power was 500 μW. We multiplied the retrieved signals in both channels by 10 for clarity. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

10. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Experimental results on long time storage. Information carried by the probe pulse (sent in from Ch1) is written into and stored in the coherence of atoms. After 1.2 s, we turn on a much stronger control field (about 6 mW) in a different location of the cell (Ch2) and the retrieved signal is recorded. The retrieved part was recorded in a separate trace with much more average time. The control power in Ch1 was about 240 μW. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

11. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Experimental result of the double exponential decay of the optical memory. Retrieved pulse height was measured at different storage times. (a) The red solid line was a double exponential function with the two time constants Tshort about 4.5 ms and Tlong 120 ms. (b) The same experiment data but after 100 ms. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703

12. Date of download: 9/19/2016 Copyright © 2016 SPIE. All rights reserved. Relaxation measurements of T1 (a) and T2 (b) using the “relaxation in the dark” method. 24 The fitting (red solid curves) gives decay time constants of T1 about 83 ms and T2 about 6.8 ms. Figure Legend: From: Amplified slow light beam splitter and 1 s optical memory Opt. Eng. 2014;53(10):102703. doi:10.1117/1.OE.53.10.102703